private void Sort(RecordsReader recordsReader, int field, StreamWriter output,
int workersCount, long bufferSizeInBytesPerWorker)
{
Stopwatch sortSw = new Stopwatch();
sortSw.Start();
RecordsBuffer firstBlock;
int blockCount = workersCount > 1
? SortBlocksParallel(recordsReader, field, workersCount, out firstBlock)
: SortBlocksSequential(recordsReader, field, out firstBlock);
sortSw.Stop();
if (blockCount == 1)
{
RecordsWriter recordsWriter = new RecordsWriter(output);
recordsWriter.WriteRecords(firstBlock);
}
else
{
Console.WriteLine($"{blockCount} blocks sorted in {sortSw.Elapsed}");
Console.WriteLine("Merging...");
Stopwatch mergeSw = new Stopwatch();
mergeSw.Start();
MergeBlocks(blockCount, field, output, bufferSizeInBytesPerWorker);
mergeSw.Stop();
Console.WriteLine($"{blockCount} blocks merged in {mergeSw.Elapsed}");
_tempStreams.ClearBlocks();
}
}
private void MergeBlocks(int blockCount, int field, StreamWriter output, long bufferSizeInBytes)
{
long blockSize = bufferSizeInBytes / (blockCount + 1);
List <Stream> blockStreams = new List <Stream>();
try
{
List <IEnumerator <Record> > blockRecordsEnumerators = new List <IEnumerator <Record> >();
for (int i = 0; i < blockCount; i++)
{
Stream blockStream = _tempStreams.OpenBlockStream(i);
blockStreams.Add(blockStream);
StreamReader blockStreamReader = new StreamReader(blockStream);
RecordsReader blockReader = new RecordsReader(blockStreamReader, blockSize);
blockRecordsEnumerators.Add(blockReader.ReadRecords().GetEnumerator());
}
using (BufferedRecordsWriter recordsWriter = new BufferedRecordsWriter(output, blockSize))
{
MergeBlocks(blockRecordsEnumerators, recordsWriter, field);
}
}
finally
{
foreach (Stream s in blockStreams)
{
s.Dispose();
}
}
}
private int SortBlocksSequential(RecordsReader recordsReader, int field, out RecordsBuffer firstBlock)
{
int blockIndex = 0;
firstBlock = null;
IEnumerable <RecordsBuffer> blocks = recordsReader.ReadBlocks();
foreach (RecordsBuffer block in blocks)
{
block.Sort(field);
if (blockIndex == 0)
{
if (recordsReader.IsLastBlock)
{
firstBlock = block;
return(1);
}
}
WriteBlock(block, blockIndex);
Console.WriteLine($"Block {blockIndex} sorted");
blockIndex++;
}
return(blockIndex);
}
private int SortBlocksParallel(RecordsReader recordsReader, int field, int workersCount,
out RecordsBuffer firstBlock)
{
firstBlock = null;
IEnumerator <RecordsBuffer> blocks = recordsReader.ReadBlocks().GetEnumerator();
if (!blocks.MoveNext())
{
return(0);
}
if (recordsReader.IsLastBlock)
{
firstBlock = blocks.Current;
firstBlock.Sort(field);
return(1);
}
int blockIndex = 0;
using (var blockCollection = new BlockingCollection <Tuple <RecordsBuffer, int> >(workersCount))
using (var sortCompletionCollection = new BlockingCollection <bool>(workersCount))
{
Task blocksReadingTask = Task.Factory.StartNew(() =>
{
do
{
blockCollection.Add(new Tuple <RecordsBuffer, int>(blocks.Current, blockIndex++));
sortCompletionCollection.Add(true);
} while (blocks.MoveNext());
blockCollection.CompleteAdding();
});
Task blocksSortingTask = Task.Factory.StartNew(() =>
{
List <Task> sortTasks = new List <Task>();
try
{
while (true)
{
Tuple <RecordsBuffer, int> blockAndIndex = blockCollection.Take();
Task t = StartBlockSortingTask(blockAndIndex.Item1, blockAndIndex.Item2,
field, sortCompletionCollection);
sortTasks.Add(t);
}
}
catch (InvalidOperationException)
{
// An InvalidOperationException means that Take() was called on a completed collection
}
Task.WaitAll(sortTasks.ToArray());
});
Task.WaitAll(blocksReadingTask, blocksSortingTask);
}
return(blockIndex);
}
/// <summary>
/// Sorts big tabled data from stream by specified fields.
/// </summary>
/// <param name="input">Source data stream.</param>
/// <param name="field">Field indexes by which sorting will happen one after another.</param>
/// <param name="output">Dest data stream.</param>
public void Sort(Stream input, int[] fields, Stream output)
{
int prevField = -1;
Stream originalOutput = output;
int tempOutputFirst = fields.Length % 2;
Stream tempOutput = fields.Length > 1 ? _tempStreams.CreateTempOutputStream() : null;
int workersCount = _maxWorkersCount;
long bufferSizeInBytesPerWorker = _maxBufferSizeInBytes / workersCount;
try
{
for (int i = 0; i < fields.Length; i++)
{
Console.WriteLine($"Sorting by field {fields[i]}...");
Stopwatch stopwatch = new Stopwatch();
stopwatch.Start();
output = (i % 2) == tempOutputFirst ? tempOutput : originalOutput;
input.Position = 0;
output.Position = 0;
StreamReader sr = new StreamReader(input);
StreamWriter sw = new StreamWriter(output);
RecordsReader recordsReader = new RecordsReader(sr, bufferSizeInBytesPerWorker, prevField);
while (!recordsReader.IsEnd)
{
Sort(recordsReader, fields[i], sw, workersCount, bufferSizeInBytesPerWorker);
}
sw.Flush();
prevField = fields[i];
input = output;
stopwatch.Stop();
Console.WriteLine($"Sorting by field {fields[i]} done in {stopwatch.Elapsed}");
}
}
finally
{
if (tempOutput != null)
{
tempOutput.Dispose();
}
}
}
